1. Field of the Invention
The present invention concerns nucleic acid sequences which code for carcinoembryonic antigen (CEA) antigen family peptide sequences.
2. Background Information
Carcinoembryonic antigen was first described by Gold and Freedman, J. Exp. Med., 121, 439-462, (1965). CEA is characterized as a glycoprotein of approximately 200,000 molecular weight with 50-60% by weight of carbohydrate. CEA is present during normal human fetal development, but only in very low concentration in the normal adult intestinal tract. It is produced and secreted by a number of different tumors.
CEA is a clinically useful tumor marker for the management of colorectal cancer patients. CEA can be measured using sensitive immunoassay methods. When presurgical serum levels of CEA are elevated, a postsurgical drop in serum CEA to the normal range typically indicates successful resection of the tumor. Postsurgical CEA levels that do not return to normal often indicate incomplete resection of the tumor or the presence of additional tumor sites in the patient. After returning to normal levels, subsequent rapid rises in serum CEA levels usually indicate the presence of metastages. Slower postsurgical rises from the normal level are most often interpreted to indicate the presence of new primary tumors not previously detected. Post surgical management of colon cancer patients is thus facilitated by the measurement of CEA.
CEA is a member of an antigen family. Because of this, the immunoassay of CEA by presently available methods is complicated by the fact that CEA is but one of several potentially reactive antigens. There have been at least sixteen CEA-like antigens described in the literature. Since some of these appear to the same antigen described by different investigators, the actual number of different antigens is somewhat less than this number. Nonetheless, there is a complex array of cross-reactive antigens which can potentially interfere with an immunoassay of the CEA released by tumors. It is known that serum levels of CEA-like antigens are elevated in many non-cancerous conditions such as inflammatory liver diseases and also in smokers. It is important that immunoassays used for the monitoring of cancer patient status not be interfered with by these other CEA-like antigens. Conversely, it is important to be able to distinguish the antigens by immunoassays because of the possibility that different tumor types may preferentially express different forms of CEA. If so, then the ability to reliably measure the different forms of CEA can provide the means to diagnose or more successfully treat different forms of cancer.
The members of the "CEA family" share some antigenic determinants. These common epitopes are not useful in distinguishing the members of the antigen family and antibodies recognizing them are of little use for measuring tumor-specific CEA levels.
U.S. Pat. No. 3,663,684, entitled "Carcinoembryonic Antigen and Diagnostic Method Using Radioactive Iodine", concerns purification and radioiodination of CEA for use in a RIA.
U.S. Pat. No. 3,697,638 describes that CEA is a mixture of antigens (components A and B in this case). U.S. Pat. No. 3,697,638 mentions methods for separating and radioiodinating each component and their use in specific RIA's.
U.S. Pat. No. 3,852,415, entitled "Compositions for Use in Radioimmunoassay, as Substitute for Blood Plasma Extract in Determination of Carcinoembryonic Antigen" relates to the use of a buffer containing EDTA and bovine serum albumin as a substitute for plasma as a diluent for CEA RIA's.
U.S. Pat. No. 3,867,363, entitled "Carcinoembryonic Antigens", is directed to the isolation of CEA components A and B, their labelling and use in a RIA.
U.S. Pat. No. 3,927,193, entitled "Localization of Tumors by Radiolabelled Antibodies", concerns the use of radiolabelled anti-CEA antibodies in whole body tumor imaging.
U.S. Pat. No. 3,956,258, entitled "Carcinoembryonic Antigens", relates to the isolation of CEA components A and B.
U.S. Pat. No. 4,086,217, entitled "Carcinoembryonic Antigens", is directed to the isolation of CEA components A and B.
U.S. Pat. No. 4,140,753, entitled "Diagnostic Method and Reagent", concerns the purification of a CEA isomer called CEA-S1 and its use in a RIA.
U.S. Pat. No. 4,145,336, entitled "Carcinoembryonic Antigen Isomer", relates to the antigen CEA-S1.
U.S. Pat. No. 4,180,499, entitled "Carcinoembryonic Antigens", describes a process for producing CEA component B.
U.S. Pat. No. 4,228,236, entitled "Process of Producing Carcinoembryonic Antigen", is directed to the use of the established cell lines LS-174T and LS-180 or clones or derivatives thereof for the production of CEA.
U.S. Pat. No. 4,272,504, entitled "Antibody Adsorbed Support Method for Carcinoembryonic Antigen Assay", concerns two concepts for the radioimmunoassay of CEA. First, U.S. Pat. No. 4,272,504 relates to a sample pretreatment in the form of heating to 65.degree. to 85.degree. C. at pH 5 to precipitate and eliminate extraneous protein. Second, it describes the use of a solid phase antibody (either on beads or tubes) as a means to capture analyte and radiolabelled CEA tracer.
U.S. Pat. No. 4,299,815, entitled "Carcinoembryonic Antigen Determination", concerns diluting a CEA sample with water and pretreating by heating to a temperature below which precipitation of protein will occur. The pretreated sample is then immunoassayed using RIA, EIA, FIA or chemiluminescent immunoassay.
U.S. Pat. No. 4,349,528, entitled "Monoclonal Hybridoma Antibody Specific for High Molecular Weight Carcinoembryonic Antigen", is directed to a monoclonal antibody reacting with 180 kD CEA, but not with other molecular weight forms.
U.S. Pat. No. 4,467,031, entitled "Enzyme-Immunoassay for Carcinoembryonic Antigen", relates to a sandwich enzyme immunoassay for CEA in which the first of two anti-CEA monoclonal antibodies is attached to a solid phase and the second monoclonal is conjugated with peroxidase.
U.S. Pat. No. 4,489,167, entitled "Methods and Compositions for Cancer Detection", describes that CEA shares an antigenic determinant with alpha-acid glycoprotein (AG), which is a normal component of human serum. The method described therein concerns a solid-phase sandwich enzyme immunoassay using as one antibody an antibody recognizing AG and another antibody recognizing CEA, but not AG.
U.S. Pat. No. 4,578,349, entitled "Immunoassay for Carcinoembryonic Antigen (CEA)", is directed to the use of high salt containing buffers as diluents in CEA immunoassays.
EP 113072-A, entitled "Assaying Blood Sample for Carcinoembryonic Antigen--After Removal of Interfering Materials by Incubation with Silica Gel", relates to the removal from a serum of a plasma sample of interfering substances by pretreatment with silica gel. The precleared sample is then subjected to an immunoassay.
EP 102008-A, entitled "Cancer Diagnostics Carcinoembryonic Antigen--Produced from Perchloric Acid Extracts Without Electrophoresis", relates to a procedure for the preparation of CEA from perchloric acid extracts, without the use of an electrophoresis step.
EP 92223-A, entitled "Determination of Carcinoembryonic Antigen in Cytosol or Tissue--for Therapy Control and Early Recognition of Regression", concerns an immunoassay of CEA, not in serum or plasma, but in the cytosol fraction of the tumor tissue itself.
EP 83103759.6, entitled "Cytosole-CEA-Measurement as Predictive Test in Carcinoma, Particularly Mammacarcinoma", is similar to EP 92223-A.
EP 83303759, entitled "Monoclonal Antibodies Specific to Carcinoembryonic Antigen", relates to the production of "CEA specific" monoclonal antibodies and their use in immunoassays.
WO 84/02983, entitled "Specific CEA-Family Antigens, Antibodies Specific Thereto and Their Methods of Use", is directed to the use of monoclonal antibodies to CEA-meconium (MA)-, and NCA-specific epitopes in immunoassays designed to selectively measure each of these individual components in a sample.
All of the heretofore CEA assays utilize either monoclonal or polyclonal antibodies which are generated by immunizing animals with the intact antigen of choice. None of them address the idea of making sequence specific antibodies for the detection of a unique primary sequence of the various antigens. They do not cover the use of any primary amino acid sequence for the production of antibodies to synthetic peptides or fragments of the natural product. They do not include the concept of using primary amino acid sequences to distinguish the CEA family members. None of them covers the use of DNA or RNA clones for isolating the genes with which to determine the primary sequence.
______________________________________ DEFINITIONS ______________________________________ Nucleic Acid Abbreviations A adenine G guanine C cytosine T thymidine U uracil Amino Acid Abbreviations: Asp aspartic acid Asn asparagine Thr threonine Ser serine Glu glutamic acid Gln glutamine Pro proline Gly glycine Ala alanine Cys cysteine Val valine Met methionine Ile isoleucine Leu leucine Tyr tyrosine Phe phenylalanine Trp tryptophan Lys lysine His histidine Arg arginine ______________________________________
Nucleotide--A monomeric unit of DNA or RNA containing a sugar moiety (pentose), a phosphate, and a nitrogenous hetercyclic base. The base is linked to the sugar moiety via the glycosidic carbon (1' carbon of the pentose) and that combination of base and sugar is called a nucleoside. The base characterizes the nucleotide. The four DNA bases are adenine ("A"), guanine ("G"), cytosine ("C"), and thymine ("T"). The four RNA bases are A, G, C and uracil ("U").
DNA Sequence--A linear array of nucleotides connected one to the other by phosphodiester bonds between the 3' and 5' carbons of adjacent pentoses.
Functional equivalents--It is well known in the art that in a DNA sequence some nucleotides can be replaced without having an influence on the sequence of the expression product. With respect to the peptide this term means that one or more amino acids which have no function in a particular use can be deleted or replaced by another one.
Codon--A DNA sequence of three nucleotides (a triplet) which encodes through mRNA an amino acid, a translation start signal or a translation termination signal. For example, the nucleotide triplets TTA, TTG, CTT, CTC, CTA and CTG encode the amino acid leucine ("Leu"), TAG, TAA and TGA are translation stop signals and ATG is a translation start signal.
Reading Frame--The grouping of codons during translation of mRNA into amino acid sequences. During translation, the proper reading frame must be maintained. For example, the sequence GCTGGTTGTAAG may be translated in three reading frames or phases, each of which affords a different amino acid sequence ##STR1##
Polypeptide--A linear array of amino acids connected one to the other by peptide bonds between the alpha-amino and carboxy groups of adjacent amino acids.
Genome--The entire DNA of a cell or a virus. It includes inter alia the structural genes coding for the polypeptides of the cell or virus, as well as its operator, promoter and ribosome binding and interaction sequences, including sequences such as the Shine-Dalgarno sequences.
Structural Gene--A DNA sequence which encodes through its template or messenger RNA ("mRNA") a sequence of amino acids characteristic of a specific polypeptide.
Transcription--The process of producing mRNA from a structural gene.
Translation--The process of producing a polypeptide from mRNA.
Expression--The process undergone by a structural gene to produce a polypeptide. It is a combination of transcription and translation.
Plasmid--A non-chromosomal double-stranded DNA sequence comprising an intact "replicon" such that the plasmid is replicated in a host cell. When the plasmid is placed within a unicellular organism, the characteristics of that organism may be changed or transformed as a result of the DNA of the plasmid. For example, a plasmid carrying the gene for tetracycline resistance (Tet.sup.R) transforms a cell previously sensitive to tetracycline into one which is resistant to it. A cell transformed by a plasmid is called a "transformant".
Phage or Bacteriophage--Bacterial virus, many of which consist of DNA sequences encapsulated in a protein envelope or coat ("capsid protein").
Cloning Vehicle--A plasmid, phage DNA or other DNA sequence which is capable of replicating in a host cell, which is characterized by one or a small number of endonuclease recognition sites at which such DNA sequences may be cut in a determinable fashion without attendant loss of an essential biological function of the DNA, e.g., replication, production of coat proteins or loss of promoter or binding sites, and which contains a marker suitable for use in the identification of transformed cells, e.g., tetracycline resistance or ampicillin resistance. A cloning vehicle is often called a vector.
Cloning--The process of obtaining a population of organisms or DNA sequences derived from one such organism or sequence by asexual reproduction.
Recombinant DNA Molecule or Hybrid DNA--A molecule consisting of segments of DNA from different genomes which have been joined end-to-end outside of living cells and have the capacity to infect some host cell and be maintained therein.
cDNA Expression Vector--A procaroytic cloning vehicle which also contains sequences of nucleotides that facilitate expression of cDNA sequences in eucaroytic cells. These nucleotides include sequences that function as eucaryotic promoter, alternative splice sites and polyadenylation signals.
Transformation/Transfection--DNA or RNA is introduced into cells in such a way as to allow gene expression. "Infected" referred to herein concerns the introduction of RNA or DNA by a viral vector into the host.
"Injected" referred to herein concerns the microinjection (use of a small syringe) of DNA into a cell.
CEA antigen family (CEA gene family)--a set of genes (gene family) and their products (antigen family) that share nucleotide sequences homologous to partial cDNA LV-7 (CEA-(a)) and as a result of theses similarities also share a subset of their antigenic epitopes. Examples of the CEA antigen family include CEA (=CEA-(b)), transmembrane CEA (TMCEA)=CEA-(c) and normal crossreacting antigen NCA (=CEA-(d)).